Generally, a cylindrical alkaline battery comprises a cylindrical cathode canister having a closed bottom, with a ring-shaped positive electrode mixture stored within the cathode canister and a gelled negative electrode mixture stored centrally within the cathode canister, with a cylindrical separator, having a closed bottom, set between the positive electrode mixture and the gelled negative electrode mixture, and a current collector provided on the opening of the cathode canister. The current collector comprises a negative terminal plate, a negative electrode collector and a sealing gasket. The negative terminal plate seals the opening of the cathode canister by the sealing gasket.
FIG. 6 shows a conventional gasket 40, used in sealing cylindrical alkaline batteries, comprising a boss part 42, a canister-contact part 43, a disk-shaped part 44 and a shear-inducible ring-shaped thin part 45. The boss part 42 has a central hole 41 through which a negative electrode collector is inserted. The canister-contact part 43 is affixed to and thus touches the inner side of the battery canister. The disk-shaped part 44 extends radially from the outer periphery of the boss part 42. The shear-inducible ring-shaped thin part 45 connects the boss part 42 to the disk-shaped part 44. When pressure within the alkaline battery rises due to forming gas, the ring-shaped thin part 45 breaks to release the gas from the alkaline battery canister, thus preventing the battery from being damaged.
A stress-buffering part 47 is formed close to the canister-contact part 43, on the outer periphery of the gasket. The stress-buffering part 47 is crooked in shape and projects downward (as seen in FIG. 6). Upon the opening of the cathode canister being sealed, this stress-buffering part 47 becomes radially deformed in absorbing the stress placed on the ring-shaped thin part 45. The stress-buffering part 47 is thinly formed to be flexible, so as to enhance its stress-absorption property. The structure of the gasket 40 is disclosed in Patent Document 1. The stress-buffering part 47 of the gasket 40, as seen cross-sectionally in FIG. 6, is U-shape bent. Other conventional gaskets, shown cross-sectionally, are S-shaped bent.
Patent Document 1: JP-A-2007-80574